Voice synthesizing devices which enable articulation of speech on an interim or permanent basis, utilizing an external source of sound, are most useful for post operative care of patients in hospitals where vocal communication is difficult or impossible. Providing such patients with a disposable, portable and battery operated unit from which the "voice" sound is generated, calls for an effective but economical unit which will be easy to use and safe in oxygen enriched atmospheres often found in hospitals.
It is therefore an important object of the present invention to provide a safe and low cost voice synthesizer unit which is useful for post operative care of patients, especially in environments with high ambient noise.